Woodworking machines, such as planers and sanders, as well as various other dimensionally adjustable tools employ digital readouts that measure the height, length or thickness of the piece on which the tool is working. Properly calibrating the readout device tends to be problematic. For example, in planers and sanders, the readout is typically mounted to a height-adjustable cutting head. In order to avoid damage to the cutting blades, this head is normally not allowed to engage the wood-supporting table of the machine. As a result, it is virtually impossible to properly calibrate the machine by simply adjusting the height of the head alone. A representative or previously planed board first must be accurately measured using calipers or a similar instrument. This measurement must then be physically entered into the readout, which calibrates the instrument. This procedure requires extra, independent measurements and is tedious, time-consuming and subject to caliper misreadings and, as a result, inaccurate calibration results. Moreover, readouts capable of such data entry are fairly complex and expensive instruments.
Conventional digital readouts exhibit additional shortcomings. Many users prefer for the measured readings to appear in a fractional format on the readout. However, decimally-based readout devices typically have a much higher resolution than fractionally-based readouts. Decimal displays normally have a resolution of one-thousandth inch or less. Fractional displays, however, normally exhibit fractions no smaller than one-sixty fourth inch (i.e. 0.015625 inch). This is more than fifteen times greater than the resolution that the typical readout is capable of producing. As a result, the user is unable to obtain the most accurate measurements possible.
The lack of resolution in conventional digital measuring systems is compounded because the fractional dimensions are typically programmed to initially appear on the display at the midpoint of the closest decimal equivalent and the decimal that is equivalent to the immediately preceding fraction. For example, in a fractional readout display, the fraction one-sixteenth ( 1/16) (having a decimal equivalent of 0.063) is normally programmed to appear on the readout display at an actual dimension of 0.047, which is the mid-point between 0.031 (the decimal equivalent of 1/32) and 0.063. The fractional equivalents therefore visually appear on the display at measured values significantly below and above the decimal equivalents. This can result in measurements that are imprecise and unsatisfactory. Moreover, conventional digital readouts do not provide an accurate and reliable, yet east to read and understand correlation between corresponding decimal and fractional equivalents. The clarity and accuracy of such digital measuring systems needs to be significantly improved, especially for persons desiring to employ a fractional display.